Sukuna does die in the manga. The way it happens is quite dramatic and ties in with many other elements of the story, adding depth and tension to the overall narrative.
Since I don't have enough information about the particular novel, I can't provide the last name of Gordo. It could be that this is a relatively unknown or very specific reference within a certain genre or niche of literature. Maybe if you could give some more details about the type of novel or the plot, it would be easier to answer.
No. Ryomen Sukuna is a fictional character from Japanese mythology and modern manga/anime. He doesn't have a basis in a true historical event or person.
Nope. Ryomen Sukuna has no basis in reality. It's a product of the creative minds of the writers and illustrators who designed a captivating fictional character for the enjoyment of the audience.
The scariest might be the story of the headless miner. It's said that he lost his head in a mining explosion. His headless body is seen wandering the tunnels, and sometimes people can feel his cold presence even when they can't see him. It gives a really eerie feeling especially when you're in the dark and narrow mine passages.